1. Field of the Invention
The present invention relates generally to multi-sensor systems, and particularly to multi-sensor systems for counting and identifying objects in close proximity.
2. Technical Background
In a typical casino environment, gaming chips are initially loaded in a secure area such as a vault. The gaming chips are subsequently transferred in trays to an area commonly referred to as the “Pit.” The trays are then transferred to the gaming tables as needed in accordance with the course of business. Along each step there is a need for the casino personnel to count the chips on the tray, determine the value of the tray and take responsibility for the tray. The dollar value that a complete tray represents can be quite high.
When managing their trays, dealers usually place chips of the same color in a given column to simplify accounting. Chips are separated into groups comprising, for example, 20 chips, the groups being separated by spacers called “lammers.” The lammers allow casino personnel to quickly and easily count the number of chips in a column. For example, a sixty (60) chip column, of course, would include three groups of twenty (20) chips, with each group being separated by a lammer. A column may be include 50 to 60 chips. If a column is not completely filled, the remaining chips in the last group (less than 20) will usually not be terminated by a lammer.
Assuming for the sake of example that there are twelve (12) columns of gaming chips in a tray, a single tray may be valued in the tens of thousands of dollars. Accordingly, chip security and chip authentication is a significant issue for casino management. Because manual efforts to improve security and authentication have historically provide to be inadequate, casino managers are increasingly turning to automated technology based solutions.
In one approach, system designers are considering the use of electronic identification devices disposed in the gaming chip itself. By using embedded technology such as this, casino managers are hoping to reduce the incidence of counterfeiting, improve chip security and authentication, improve its operations in handling, tracking and accounting for chips, monitor dealer performance and gaming table efficiencies, and offer players additional services.
Gaming chips using embedded RFID devices seem to offer much promise in realizing a serviceable gaming chip having an electronic device embedded therein. For example, an UHF RFID system of this type is introduced in U.S. Pat. No. 5,651,458. However, the system in the '458 patent is not enabled because the patentee fails to show how a 915 MHz system may be implemented in a gaming chip. In fact, the only disclosure is directed to a system known as “Supertag.” At minimum, the Supertag 915 MHz antenna requires a minimum footprint greater than approximately 3-4 inches. To further drive the point home, no one has been able to successfully make and/or use an operable gaming chip and system at the 915 MHz frequency to date.
On the other hand, some are considering the use of gaming chips having inductively coupled high frequency HF RFID devices operating at 13.56 MHz in accordance with ISO 15693 standards. These so-called HF RFID devices would be programmed to include a unique ID number, an authentication code, casino-specific data and a monetary value which may be set when issued by the Casino.
Unfortunately, some of the HF RFID devices under consideration also experience drawbacks. For example, conventional high frequency technology does not guarantee a 100% error free tracking. Most of the errors being of the “false negative” type. i.e., a failure to detect a chip that is present. As noted above, HF RFID systems employ magnetic field coupling to track the embedded devices. Chips having inductively coupled devices may be susceptible to de-tuning when in close proximity with other chips of the same type. Accordingly, conventional techniques do not perform well when the chips are stacked or disposed in trays. Furthermore, the simple single loop couplers used in most HF RFID installations produce fields that have “holes” or “nulls” where there is insufficient signal to properly energize and read all of the chips.
Other types of sensors have been proposed for counting chips in the tray. In one approach, a photocell sensor has been disposed under each chip position. In another approach, an ultrasonic sensor was provided for each column of chips. Alternatively, an ultrasonic sensor is provided for each column of chips and a color sensor is provided for the first chip of each column. Unfortunately, none of the aforementioned approaches have been particularly successful.
What is needed, therefore, is a multi-sensor system for counting and identifying either stacked chips or a group of chips arranged in a tray.